Pump



Dec. 10, 1935." M. E. CROWLEY PUMP Filed Feb. 15, 19 33 I'NVENTOR, ILLARE. CROWLEY.

A TTORNEY Patented Dec. 10, 1935 PATENT PUIWP Millard E. Crowley, SanFrancisco, Calif., as-

signor of one-half to Blake F. Hopkins, San

Francisco, Calif.

Application February 18, 1933, Serial No. 657,335

10 Claims.

My invention relates to pumps of the reciprocating type, andparticularly to air compressors, this application being a continuationin part, of my copending application, Serial No. 586,433, now

forfeited, insofar as it relates to common subject matter.

Among the objects of this invention are: To provide a combined pistonand mechanically -operated valve for reciprocating pumps; to provide a.mechanically operated intake valve which is applicable to compressorseven in very small sizes; to provide a high efliciency pump of thecompressor type; to provide an air pump of small size which can be runat high speed; and to provide a pump of high output which is small insize and economical in manufacture and operation.

Other objects of my invention will be apparent or will be specificallypointed out in the descripdo not limit myself to the embodiment of myinvention herein described, as various forms may be adopted within thescope of the claims.

Referring to the drawing:

Figure 1 is a partly diagrammatic sectional view of a pump embodying myinvention, the plane of section being taken through the pump cylinder.

Figure 2 is a side elevation of in Figure 1.

- Figure 3 is a diagrammatic sectional view showing a section throughthe cylinder of a modified form of pump embodying 'my invention.

Figure 4 is a similar view showing a modified form of piston'as appliedto the pump of Figure 1.

In general terms the pump of my invention the pump shown comprises theusual cylinder. within which is,

fitted a piston having a head of such form that it may be tilted withinthe cylinder. Means are provided for reciprocating the piston within thepump and tilting it within the cylinder in concurrent cycles, so that onone stroke of the piston, which may be called the advance stroke, thepiston contacts with the entire cylinder wall, while on the other orreturn stroke the tilted piston contacts only a portion of the wall,permitting thejfluid which is to be pumped to pass by the piston intothe space beneath it. The "lting piston head therefore operates not onlyas a" piston but as a mechanically operated valve whose cycle ofoperation is properly timed with respect to the piston stroke.

Reciprocating pumps operating on compressible fluid, i. e., compressors,are ineiilcient at best.

tion forming a part of this specification, but I Even in pumps of largesize, where there is ample room for the mounting of valves and operatingmechanism, the thermodynamic cycle is such that high efliciency isdiificult of attainment, but in the small sizes, where considerations ofspace and expense makes the use of mechanically operated valves of theusual poppet or slide-valve type impracticable, and resort is had tospring controlled intake valves operated bythe pressure of the externalair, the eflic'iency drops with startling rapidity. I

One of the major causes of the low efliciency is the fact that asuflicientlyhigh vacuum must be established within the cylinder to holdthe valve open during the intake portion of the stroke, so that at thebeginning ofv the compression stroke the gas within the cylinder is atless than atmospheric pressure. Furthermore, unless great care is usedin design the tendency oi the spring to close the intake valve keeps theeffective port small, and the gas must enter at high velocity, causingwire-drawing" with consequent loss of efliciency. The result is that avery small amount of compressed air is obtained when the power expendedto operate the apparatus is considered. The outlet valve, through whichthe gas passes at low. velocity, and usually into a tank or receiverwhere the pressure is relatively high, although causing a loss inefliciency, is not nearly as important a factor as the intake valve.This invention is primarily directed toward reducing intake valvelosses, although simplicity of construction is also an important factor.

In the drawing a preferred form of the invention is shown, this drawingbeing in semidiagrammatic form so that the essential features of theinvention may not be obscured by nonessential detail. I

The compressor illustrated is a small size, relatively high speed type,adapted for operation by 49 a fractional horse power electric motor I.The motor is mounted upon a rectangular air tank or receiver 2, whichserves as a base and mounting for both the motor and the compressor.

A fly wheel I is preferably provided on the motor shaft in order toreduce vibration, a crank pin 5 being aflixed to the fly wheel. Suitablecounter weighting for the pin and other reciprocating parts may beprovided within the rim 0! the fly wheel, in accordance with well knownpractice, but this is not shown as it is a mere mechanical expedientwell known in the art.

A cylinder. 6 is mounted upon one face of the receiver 2 by meansof-straps or clamps I. The cylinder is conveniently formed or seamlesdrawn tubing, and may be of round, rectangular, or other cross section,as convenience may dictate.-

Journaled on the pin Sand extending into the cylinder is a pistoncomprising a connecting-rod 9, rigidly secured to a piston head iii. Thelatter is preferably relatively thin'and flat, and fits within .thecylinder with sufficient clearance so that it may tilt freely withoutbinding. It is preferably, although not necessarily, provided with a cupleather I I, which forms a seal with the wall of the cylinder. The cupleather may be of leather, rawhide, fiber, or other conventionalmaterial.

In the form of the invention illustrated in Figure 1, the piston head isdisposed at an oblique angle to the piston rod. This angle may bereferred to as the fixed angle" or' angle of cock, and measured asbetween the axis of the connecting-rod and a perpendicular erected tothe face of the piston; The proper magnitude of the fixed angle isdependent on the length of the connecting-rod and the throw of thecrank, and is preferably such that the plane of the piston head isnormal to the cylinder axis when the piston is in the position shown inthe drawing by the full line, i. e., when the piston has completedapproximately one-half of the compression stroke, it being noted thatthe cylinder in this case is mounted with its axis perpendicular to andintersecting the axis of the drive crank. It follows from thisarrangement that immediately thepiston passes beyond this midpoint ofits down stroke it starts to tilt, the tilt increasing to that shown inthe dotted line l2 of Figure 1 at the end of the stroke. Up to theend ofthe down stroke the cup leather has remained in contact with thecylinder wall, compressing the air beneath it. Beyond this point thetilt continues to increase,

. so that one edge of the piston head clears the wall shown by thedot-and-dashlines H of the figure.

. The operation and effectiveness of the device depend on the asymmetrictilting of the piston on the two strokes of the pump. Thus during thecompression or down stroke the angle of tilt as between the'piston headand the perpendicular to the axis of the cylinder is relatively small sothat the cup washer ll, owing to its slight flexibility, maintainscontact with the wall during substantially the entire stroke. At thebottom of the stroke the tilt rapidly increases, the washer breaking itscontact with one side of the cyliniderbcfore the piston has risenappreciably, and the gap thus formed remains open during the entireintake or up stroke. At the top of the stroke the tilt rapidly decreasesagain, and the cup washer contacts the entire periphery of thecylindennmintaining' this contact throughout the down stroke. Where thediameter of the cylin- Ur is large the mere difference in area of thepening between the piston and the cylinder walls the two strokes issuflicient to allow operation the device without a cup washer althoughreduced eiheie'ncmq For best operation; however, the cup washer shouldbe used, and the amountof tilt should be so related to the flexibilityof the washer as to obtain the conditions lbr the cmdltion of maximumemciency the clearance between the piston head and the cyl-"lniierireedatthe' lower limit of the stroke should be a minimum. rmthisreason it is preferable clined surface, the degree of inclination beingsubstantially equal to the fixed angle of the piston head to theconnecting-rod.

The outlet valve of the pump may conveniently be carried by the lowercylinder head. A conventional type of valve is shown, a valve seat l6being threaded into an opening through the block l5. The valve I1 isheld against the seat by a spring i9. Connection -with the receiver ismade through a nipple 20 and elbow 2|.

The shape of the piston head must, of course, correspond substantiallywith the cross section of the cylinder. As has been stated above, thecylinder may be round, square, or rectangular, or, in fact, of anyshape. A square or rectangular piston has the advantage of giving themaximum area of opening between the piston and cylinder wall with aminimum differential in the amount of tilt. 'On the other hand, it issomewhat more diflicult to maintain a good seal at the corners of acylinder having interior angles, and a round cylinder and pistonis'advantageous from this point of view. Both types of cylinder havebeen used in practice, and have shown approximately the same efficiency.Because of its ease in manufacture, the round cylinder is probably to bepreferred but this is a matter which does not essentially affect theinvention.

It will be observed that the operation of the device depends upon therocking of the piston through a cycle concurrent and synchronous withits cycle of reciprocation, through an are which is asymmetrical withrespect to the cylinder axis. Where thisrocking is achieved in theobvious manner, 1. e., by the use of a rigid connection between thepiston head and the connecting rod, this involves as a corollary thefact that the piston head is tilted at anoblique angle to the axis ofthe cylinder when at the end of the stroke.

Another arrangement. wherein the condition mentioned may be fulfilled isshown in the diagrammatic drawing of Figure 3. In this case the cylinder6 is tilted with respect to the normal through the axis of rotation ofthe crank, i. e., the axis of the cylinder is tangent to a circle drawnwith the axis of rotation of the crank as a center. Under thesecircumstances the connecting-rod 8' is mounted perpendicular to thepiston head It).

'The attitude of the piston on the return stroke is shown by thedot-and-dash line II.

The actual magnitude of the tilt used depends very largely on thedimensions of the pump, and

upon the method of obtaining the seal. In the type shown in Figure 1,where a cup leather is employed, the fixed angle of the piston head withrespect to the connecting-rod may be even greater than the maximum anglebetween the connecting-rod and the cylinder axis, so that the piston'head at no time becomes perpendicular to the axis. Thus one successfulpump utilizing this form of seal was built with a one inch crank throw,a six and one-quarter inch ccnnectlngthe same length connecting-rod andcrank throw have utilized an angle of tilt from the perpendicular ofabout ten degrees, as shown in the drawing. This would correspond, inthe form of device shown in Figure 3, to an angle of tilt of thecylinder with respect to a perpendicular dropped from the crank aids to,the center of the lower cylinder head varying between fourteen and tendegrees, the angle of the lowerpiston head being 25 is an equatorialzone of a sphere. Here the fixed angle is one-half of the maximum anglebetween the cylinder axis and the connecting-rod 26, and the arc of thezone forming the piston head is approximately the same.'

Expressed mathematically, with this form of the device, if the length ofthe connecting-rod, measured from the center of the crank pin to thecenter of the piston head is called L, and the crank throw T, the fixedangle should be one half of the angle whose tangent is T/L. This willcause the piston valve to close 'at the top of the stroke and maintainthe seal during theentire compression half of the cycle, opening rapidlyon the return stroke. l

I claim:

1. A pump comprising a cylinder having an inlet and an outlet opening inopposite ends thereof, a piston tiltable within said cylinder, a crankfor actuating said piston, and a connecting-rod joining said piston andcrank and rigidly connected to said piston, said piston being sodisposed with respect to said cylinder and connecting rod as to form anoblique angle with the axis of the cylinder when the piston is at eitherend of its stroke.

2. A pump comprising a cylinder having a inlet and an outlet opening inopposite ends thereof, a piston tiltable within said cylinder, a crankfor actuating said piston mounted with its axis intersecting the axis ofthe cylinder, and a connecting-rod journaled on said crank and rigidlyattached to said piston and forming an oblique angle with the facethereof.

3. A pump comprising a cylinder having an inlet and an outlet opening inopposite ends thereof, a combination piston and valve comprising apiston head tiltable within the cylinder, and means for reciprocatingsaid piston head within said cylinder and tilting said piston head withrespect to the axis of said cylinder in synchronous cycles, said tiltingbeing asymmetric with respect to said axis.

4. A pump comprising a cylinder having an inlet and an outlet opening inopposite ends thereof, a combination piston and valve comprising apiston head tiltable within the cylinder, means for reciprocating saidpiston head within said cylinder and tilting said piston head withrespect to the axis of said cylinder in synchronous cycles, said tiltingbeing asymmetric with respect to said axis, and means for maintaining aseal between said piston head and the wall of said cylinder duringapproximately one-half of said tilting cycle.

5. A pump comprising a cylinder having an inlet and an outlet opening inopposite, ends thereof, a combination piston and valve comprising apiston head tiltable within the cylinder, means for reciprocating saidpiston head within said cylinder and tilting said piston head withrespect to the axis of said cylinder in synchronous cycles, said tiltingbeing asymmetric with respect to said axis, and a cup leather mounted onthe face of said piston head for maintaining a seal between said pistonhead and the wall of said cylinder during approximately one-half of saidtilt- 5 ing cycle.

6. A pump comprising a cylinder having an inlet and an outlet opening inopposite ends thereof, a rigid T-shaped piston within said cylinder, anda crank whereon said piston is journaled, said cylinder being so mountedwith respect to said crank that the axis of said cylinder is tangent toa circle having the crank axis as a center 7. A pump comprising acylinder having an inlet and an outlet opening in opposite ends thereof,a piston within the cylinder comprising a connecting-rod and a pistonhead rigidly afilxed thereto, a crank whereon said connecting-rod isjournaled, said -cylinder, connecting-rod and crank being relatively somounted that said piston head forms an oblique angle with the axis ofthe cylinder when the piston is at the end of its stroke, and a head onsaid cylinder forming an angle with the cylinder walls substantiallyequal to the angle formed between the piston head and the cylinder axisat the end of the stroke.

8. A pump comprising a cylinder having an inlet and an outlet opening inopposite ends thereof, a piston head within the cylinder whose peripheryis formed substantially as the equatorial zone of a sphere, aconnecting-rod rigidly attached to said piston head, and a crank whereonsaid conecting-rod is journaled, said cylinder, connecting-rod and crankbeing relatively so disposed with respect to said piston head that the3. latter forms an oblique angle with the axis of the cylindersubstantially equal to one-half the arc of its peripheral zone when atthe end of its stroke.

9. A pump comprising a crank, a cylinder having an inlet and an outletopening in opposite ends thereof mounted with its axis intersecting theaxis of rotation of said crank, a connectingrod journaled on said crank,and a piston head within the cylinder rigidly aifixed' to saidconnecting-rod within the cylinder and formed substantially as theequatorial zone of a sphere, said piston head forming a fixed angle withthe perpendicular to said connecting rod substantially equal to one-halfof theangle whose tangent is 50 T/L, where T is the throw of the crankand L the length of the connecting-rod.

10. A pump comprising a crank, a cylinder having inlet and outletopenings at opposite ends thereof mounted with its axis intersecting theaxis 55 of rotation of said crank, a connecting rod journaled on saidcrank, and a piston head within the cylinder rigidly affixed to saidconnecting -rod within the cylinder and formed substantially as theequatorial zone of a sphere, said piston head 00 forming a fixed anglewith the perpendicular to said connecting-rod substantially equal toonehalf of the angle whose tangent is T/L, where T is the throw of thecrank and L the length of the connecting-rod, and the angle subtended at5 the center of said zone being substantially equal to said fixed angle.

MILLARD E. CROWLEY.

